DESCRIPTION: As a postdoctoral fellow with Tom Cech, the applicant developed a system in E. coli whereby a truncated lacZ transcript could be repaired by a Group I ribozyme trans-splicing reaction. As Assistant Professor in the Department of Experimental Surgery and Genetics at Duke, he now proposes to establish a tissue culture system in which he can study ribozyme targeting for the development of therapeutically useful ribozymes which could repair mutant transcripts associated with genetic disorders or inhibit the expression of deleterious genes associated with a variety of pathogens. The pilot system will employ the truncated lacZ transcript used successfully in bacteria and initial characterizations of efficiency and fidelity of trans-splicing are described. Experiments are proposed to characterize the kinetic parameters well established in vitro with those in vivo and to develop ribozymes with increased activity or specificity in the cellular setting.